1. Field of the Invention
The present invention relates to fragrance compositions having a highly desirable fruity, balsamic character and to the process for their preparation.
2. Description of the Prior Art
The resinous/oily products obtained from the needles and twigs of various conifers, such as the Canadian balsam (Abies Balsamea L.), have a pleasant balsam-like odor and their use is well known in the art of perfumery. These products are recognized to be good fixatives for perfumes used in soaps and the balsamic note is also highly desirable in the formulation of heavy, sweet, floral perfumes.
In spite of the desirable fragrance characteristics of these naturally derived products, there are problems associated with their use. The products are subject to the usual compositional variations present in natural substances and they can contain skin sensitizing agents. Also, the cost to produce consistently uniform, fragrance-grade products of this type is high. Synthetic products which have a balsamic character have therefore been much sought after by the fragrance industry.
Various derivatives of norbornane, that is, compounds containing the bicyclo[2.2.1]heptane moiety, are known to be useful as fragrances. Esters of methyl-substituted bicyclo[2.2.1]heptane- and heptene-carboxylic acids, for example, are described in U.S. Pat. No. 4,442,025 and disclosed to have fresh, natural odors. The compounds correspond to the structures ##STR1## in which the dotted line is a carbon-carbon single or double bond, R.sub.1 is a hydrogen atom or methyl group and R.sub.2 is an alkyl-or alkenyl group having 1-4 carbon atoms. Certain of the esters corresponding to the above formulas are indicated to have odors reminiscent of pine and cedar wood. There is also a general discussion of other norbornane derivatives in the reference.
To obtain the products of U.S. Pat. No. 4,442,025 the corresponding acids are first obtained and then esterified with the appropriate alcohol. 3,3-Dimethyl-bicyclo[2.2.1]heptane carboxylic acid is obtained by the peroxide-induced reaction of camphene and ethyl formate. Methyl-substituted bicyclo[2.2.1]heptene carboxylic acids are obtained by either reacting dicyclopentadiene with beta,beta-dimethylacrylylchloride or reacting cyclopentadiene with ethylcrotonate.
R. C. Kuder in an article entitled "Esters of Terpene-Derived Substituted Propionic Acids," American Perfumer and Cosmetics, 83(11):51-2(1968), indicates that the lower alkyl esters of 3,3-dimethyl-2-norbornanepropionic acid have distinctively pleasant odors. The esters are obtained by reaction of camphene with acetic anhydride to obtain the diadduct ##STR2## where R.sub.1 and R.sub.2 are hydrogen or alkyl. Reactions of this type are described in detail in U.S. Pat. Nos. 3,637,801, 3,641,144, and 3,689,537. After removal of excess acetic anhydride, the adduct can be converted by alcoholysis to the ester. Kuder indicates that the lower alkyl esters of 3,3-dimethyl-2-norbornanepropionic have very pleasant, fruity, berry-like odors with a woody character and that the methyl ester has a definite cedar wood undertone.
It would be highly desirable if balsamic fragrance products having pleasing fir needle notes were available. It would be even more advantageous if these products could be consistently produced utilizing readily available and economical starting materials.